XPUDragWidget
WIDGET_API int XPUDragWidget(
XPWidgetMessage inMessage,
XPWidgetID inWidget,
intptr_t inParam1,
intptr_t inParam2,
int inLeft,
int inTop,
int inRight,
int inBottom);
XPUDragWidget drags the widget in response to mouse clicks. Pass in not only the event, but the global coordinates of the drag region, which might be a sub-region of your widget (for example, a title bar).